Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.

Lynis - Security auditing tool for systems running Linux, macOS, BSD, and other UNIX-based systems.

Angry IP Scanner - Open-source and cross-platform network scanner designed to be fast and simple to use

Silverback - Silverback 3

Advanced IP Scanner - Advanced IP Scanner shows all network devices, gives you access to shared folders, and can even remotely switch computers off. Download it Free.

Chkrootkit - Chkrootkit is a Linux tool to locally check for signs of a rootkit. It contains: